1. Field of the Invention
The present invention relates to a ceramic slurry composition composed of a ceramic powder and an organic vehicle containing an organic binder and a solvent, a ceramic molding formed from said ceramic slurry composition, and a ceramic electronic component using said ceramic molding.
2. Description of the Related Art
A ceramic molding, in particular, a ceramic green sheet has hitherto been formed by applying a predetermined thickness of coating of a ceramic slurry made of a mixture of, for example, a ceramic powder and an organic vehicle containing an organic binder and a solvent using a doctor blade method, etc., on a carrier tape and by drying this so as to volatilize and remove the solvent.
As the organic binder used for a conventional ceramic molding, for example, thermoplastic resins can be mentioned, of which acrylic resins and polyvinyl alcohol (PVA) are typical examples.
As the manufacturing method for the ceramic molding, slip casting, injection molding, extrusion molding, thick film printing molding, etc., other than the aforementioned sheet molding, can be mentioned.
The organic binder in the ceramic slurry adsorbs on the surface of the ceramic powder and coagulates during the drying after the sheet molding so as to impart a shape maintenance property to the ceramic green sheet. In order to produce a ceramic molding having a desired strength and elongation, that is, in order to achieve sufficient adsorption and coagulation of the ceramic powder, in general, 10 to 15 parts by weight of organic binder is necessary relative to 100 parts by weight of the ceramic powder.
As a consequence, it takes much time to heat and remove the aforementioned large quantities of organic binder, and furthermore, since the degree of shrinkage accompanying the sintering of the ceramic molding is increased, deformation and warp are likely to occur in the resulting ceramic sintered material.
The present invention was made to solve the aforementioned problems. Accordingly, it is an object of the present invention to provide a ceramic molding in which a content of an organic binder is reduced and the organic binder can be heated and removed in a short time, and a ceramic electronic component using the ceramic molding.
According to an aspect of the present invention, a ceramic slurry composition composed of a ceramic powder and an organic vehicle containing an organic binder, which is made of a polyurethane resin, and a solvent is provided, wherein the organic vehicle is in an emulsion state in which fine particles of the aforementioned polyurethane resin are dispersed in the aforementioned solvent.
In the ceramic slurry composition according to the present invention, the average particle diameter of the aforementioned polyurethane resin is preferably about 300 nm or less.
The content of the aforementioned polyurethane resin in the aforementioned ceramic slurry is preferably about 8 parts by weight or less relative to 100 parts by weight of the ceramic powder.
The ceramic slurry composition according to the present invention is preferably further composed of a cross-linking agent.
The aforementioned solvent may be primarily composed of water.
Furthermore, the aforementioned polyurethane resin is preferably a resin selected from the group consisting of an anionic polyurethane resin, a nonionic polyurethane resin, and an anionic and nonionic polyurethane resin.
According to another aspect of the present invention, a ceramic molding produced by forming the aforementioned ceramic slurry composition of the present invention into a predetermined shape is provided. The aforementioned ceramic molding may be a ceramic green sheet produced by forming the aforementioned ceramic slurry into a sheet and by drying the resulting sheet.
According to another aspect of the present invention, a ceramic electronic component including a ceramic element and terminal electrodes formed so as to contact with the aforementioned ceramic element is provided, wherein the aforementioned ceramic element is produced by baking the ceramic molding of the present invention.
According to another aspect of the present invention, a ceramic electronic component including a ceramic element produced by laminating a plurality of ceramic layers, and terminal electrodes formed so as to contact with said ceramic element is provided, wherein the aforementioned ceramic layer is produced by baking the ceramic molding of the present invention.
Since the ceramic slurry composition according to the present invention is composed of the organic vehicle, which contains the organic binder made of a polyurethane resin, and which is in an emulsion state, and the solvent, the content of the organic binder in the ceramic slurry can be reduced. That is, lumps of coagulated surplus organic binder are reduced, and superior tensile strength and elongation can be provided.
In particular, when this is baked in order to produce a ceramic electronic component, the organic binder can be heated and removed in a short time, and furthermore, the degree of shrinkage accompanying the sintering of the ceramic molding is reduced, so that a high precision ceramic electronic component in which deformation and warp are reduced can be produced.
In the present invention, the average particle diameter of the polyurethane resin in the aforementioned ceramic slurry is preferably about 300 nm or less. By using fine particles of the polyurethane resin, superior tensile strength and elongation can be provided, and the content of the organic binder can be further reduced.
When the content of the polyurethane resin in the aforementioned ceramic slurry is specified to be about 8 parts by weight or less relative to 100 parts by weight of the ceramic powder, superior tensile strength and elongation can be achieved in spite of further reduced content of the organic binder.
When the aforementioned ceramic slurry is further composed of a cross-linking agent, superior tensile strength and elongation can be achieved in spite of further reduced content of the organic binder.
In particular, when the solvent in the ceramic slurry is primarily composed of water, an organic binder composed of a resin selected from the group consisting of an anionic polyurethane resin, a nonionic polyurethane resin, and an anionic and nonionic polyurethane resin can be used. Among these, when the nonionic polyurethane resin or the anionic and nonionic polyurethane resin is used, there is no fear of reaction between metal ions eluted from the ceramic powder in the ceramic slurry and hydrophilic groups of the polyurethane resin. Therefore, it is not necessary to add an excessive additive, etc., and reduction of the density of the ceramic molding can be prevented. That is, the increase of pore and increase in pore diameter in the ceramic element produced by baking the ceramic molding can be prevented.